Vitamin A has been shown to play a role ln normal growth, cell differentiation, reproduction and vision. Much is known about the pathology of vitamin A deficiency, however, the molecular basis of the mechanism of action Is only clearly understood In the visual cycle. With the recent cloning of the nuclear retinoid acid receptor it is very Likely that retinoid acid and potentially retinol can Interact with specific genes via the nuclear receptors causing modulation of transcription. We propose to use molecular cloning techniques to Identify mRNAs which are directly modulated by vitamin A, retinol and retinolic acid in the test is of the rat. Once these transcripts have been Identified we plan (1) to molecularly characterize then; (2) examine their expression in the tests and other extratesticular tissues and cell Lines; and (3) identify retinoid specific sequences In the promoter of a representative number of retinoid- modulated genes. These experiments will provide important information pertinent to the understanding of the initial events involved In the pathological and biochemical ramifications of vitamin A nutrition.